At present, due to the development of the electronic communication industry, user devices (e.g., electronic devices, such as a cellular phone, an electronic scheduler, a personal composite terminal, and a laptop computer) have become necessities in modern society, and have become important means for transmitting rapidly changing information. Such user devices have made a user's task convenient through a GUI (Graphical User Interface) environment using a touch screen, and now provide various web-based multimedia.
A user device may be equipped with a key button that is disposed on a housing that forms an external appearance. For example, the user device may be equipped with a power key button so as to provide the user device with an ON/OFF function. Or, the user device may be equipped with a volume key so as to provide the user device with a volume function, and may be provided with various keys configured to receive a user input.